An area of significant application of drilling apparatus in both the mining and tunneling industries is in drilling holes for rock-bolting. Rock-bolting is undertaken to prevent rock falls and cave-ins, and to otherwise stabilise the tunnel or mine roof and walls.
In the mining or quarrying industries drilling apparatus are also used as part of the excavation process, for example, with holes being drilled to set explosives for blasting. Other uses include drilling small diameter holes for purposes such as stoping, and probe drilling.
Prior art drilling apparatus for use in the aforementioned situations normally includes a boom along which a percussion hammer drill slides. The boom is typically mounted longitudinally in a cradle with the drill slidably mounted on the boom. A separate feeding mechanism is provided for displacing each of the boom and the drill. In such apparatus the drill is typically moved by means of a chain or rope which goes around wheels mounted at the ends of the boom and the ends of which are fastened to the drill. The chain is moved by actuation of a hydraulic cylinder or the like. The boom, in turn, is moved with respect to the cradle by means of a hydraulic cylinder mounted between it and the cradle.
A factor relevant to the design of drilling equipment used in underground mining and tunneling is the issue of size and manoeuvrability in a confined space.
In prior art apparatus, if a 6 m hole is required to be drilled, the boom must also be 6 m long. Such a configuration is able to drill shorter holes, however, when a shorter hole is required a 6 m boom with a 2 m drill steel has 4 m of wasted boom behind the drill.
Drilling rigs attached to wheeled vehicles are often required to manoeuvre around very tight corners in underground tunnels. The length of the drilling apparatus often hinders its manoeuvrability, and collisions are frequent. Disassembly, in order to improve manoeuvrability is generally impractical.
In addition to space considerations, the drilling apparatus used in mining, tunneling and quarrying must be of robust and rugged design to cope with other aspects of the harsh environment.
Unfortunately the sliding arrangements of prior art drilling apparatus do not fully address this requirement, and have high maintenance needs. Usually the greatest damage occurs to exposed hydraulic hosing supplying the driving force to the hydraulic cylinders generating forward movement of the boom, and to the drill. Another problem area is the exposed hydraulic hose reeler. These are at constant risk of damage due to falling rocks or from being crushed by any number of the moving parts.
In addition to rock fall damage, excessive wear and tear is generated by the extreme working environment. The sliding system used to advance the drill steel into the rock is poorly suited to a situation where fine rock chips from flushing water are constantly washed over and between the wearing surfaces. Where a percussion drill is employed, this situation is compounded by the hammer action which generates significant component vibration causing acceleration of wear between moving parts. These prior art systems also have various other significant wearing parts involved in the act of moving the drill forward which are subjected to similar wear patterns.
The sliding configuration of the prior art apparatus also hinders other activities commonly engaged in as part of the tunneling or mining process, such as, for example, the application of shot-crete. Shot-crete is an extremely abrasive material, containing steel fibres suspended in concrete. This is sprayed onto the tunnel interior for roof stabilisation purposes. If shot-crete is accidentally sprayed onto the sliding surfaces of the prior art apparatus wear is accelerated, and repair costs are increased.
Another recognised area of application of the invention, primarily because of the compact nature of apparatus constructed according to the invention, is use in conjunction with bore drilling rigs which can need to be transported from one site to another on public roads and highways.
Existing configurations typically employ a tower design to drill substantially vertically downwards. Such arrangements are cumbersome and can often require considerable set up time after transport to the drill site. Further, because of the general configuration of such equipment, transportation in itself is an issue. Even partially disassembled, the movement of such equipment on public roads means heavy transport vehicles are required, the transport operation is time consuming and costly. Public inconvenience also often becomes an issue.
It is an object of the invention to provide drilling apparatus which overcomes at least some of the above identified problems with prior art apparatus, or which at least provides the public with a useful choice.